1. Field of the Invention
The present invention relates to a liquid discharge head discharging a liquid and a manufacturing method thereof.
2. Description of the Related Art
As a widely spread liquid discharge head in recent years, there has been an ink-jet head. As for an ink-jet printing apparatus mounting the ink-jet head, because the price thereof has lowered in recent years, it has become a problem how to manufacture the ink-jet head at an inexpensive price. For that sake, the miniaturization of the liquid discharge substrate is especially effective. For example, because, if the liquid discharge substrate is miniaturized, the realized number of recording device substrates as the liquid discharge substrates out of a silicon wafer increases, the cost reduction of the ink-jet head, the liquid discharge head, can be attained. Because the length of the recording device substrate in the lengthwise direction thereof is tending to extend (an ink discharge port row length increase) with the recent speeding-up of image recording, it is desirable to reduce the width of the recording device substrate in order to increase the realized number of the recording device substrates in the miniaturization thereof.
In a conventional ink-jet head, the recording device substrate is fixated on a supporting member, and the electrode of an electric wiring member is joined to the electrodes formed on the surface on the side of the recording device substrate on which side the ink discharge ports are formed. The joining portion is then sealed with a resin. However, because the electrodes of the recording device substrate are provided along the width direction of the recording device substrate, many electrodes concentrate if the width of the recording device substrate is reduced, and there is the possibility of making it difficult to connect the electric wiring member to the electrodes.
The technology of providing the electrodes on both surfaces of the recording device substrate and connecting these electrodes on both surfaces electrically through internal wiring in order to cope with the problem is described in Japanese Patent Application Laid-Open No. 2006-027108.
FIGS. 10A and 10B are schematic sectional views illustrating an example of an ink-jet head of the type that provides such electrodes on the back surface side of the recording device substrate. FIG. 10A is a schematic view of the recording device substrate viewed from the side of the surface on which discharge ports are opened (discharge port opening surface), and FIG. 10B is a schematic sectional view taken along a line 10B-10B of FIG. 10A.
Penetrating electrodes 12 penetrating a liquid discharge substrate 11 and ink supply ports 13 supplying ink from the back surface side to the front surface side of the liquid discharge substrate 11 are formed in the liquid discharge substrate 11. Heating resistors 15 generating energy for discharging ink from discharge ports 14 and electrodes 16 electrically connecting the heating resistors 15 and the penetrating electrodes 12 with each other are formed on the surface of the liquid discharge substrate 11. The ink supplied from the ink supply ports 13 reaches the discharge ports 14 through liquid paths 18 formed in the inside of an orifice formation member 17. The ink is given thermal energy from heating resistors 15 provided on the way to the liquid paths 18.
In such a case of attaining the electric conduction with the outside of a substrate using the electrodes penetrating the miniaturized liquid discharge substrate and the electrodes formed on the back surface of the substrate, a supporting member supporting the liquid discharge substrate to supply electric energy as well as ink is needed. As what can be applied as such a supporting member, there exists a substrate 61 described in Japanese Patent Application Laid-Open No. 2002-086742, as illustrated in FIG. 11. The substrate 61 is formed of a plurality of layers 64 such as green sheets, and dies 60 of print heads on the surface of the substrate 61 with mounting layers 65 put between the dies 60 and the surface. In the substrate 61, ink flow paths 63 and conduction paths 69 are formed through the plurality of layers 64. I/O pads 66, which are ends of the conduction paths 69 of one side, are provided on the top surface 62 of the substrate 61. The dies 60 are electrically connected to the I/O pads 66 with lead wires 68 for wire boding.
Now, it is known that the problem that is not suggested by the Japanese Patent Application Laid-Open No. 2002-086742 mentioned above is caused when a liquid discharge head achieving conduction between the back surface of a liquid discharge substrate and the front surface of a supporting member supporting the liquid discharge substrate using penetrating electrodes is considered. That is, because the dies 60 are mounted on the flattened front surface of the mounting layers 64 and electric conduction is realized by the wire bonding connections of the lead wires 68 to the I/O pads 66 of the top surface 62 of the substrate 61, the electric connection has no problem even if the top surface 62 has a somewhat irregular form.
However, if the liquid discharge substrate is miniaturized, electric connection by wire bonding is difficult to a certain number of terminals or more. Furthermore, if a liquid discharge substrate including penetrating electrodes as illustrated in FIG. 10B is mounted on a laminated supporting member such as the substrate 61, then the flatness around the ink supply ports of the front surface of the laminated supporting member becomes a problem. In particular, the ink supply ports of the miniaturized liquid discharge substrate and the electric connection structure are in a very near positional relationship, and consequently the influence of the force operating at the time of opening the ink supply ports on the irregularities of the front surface of the laminated supporting member becomes a large problem for the electric connection portions for which certain connection is required.